The present invention is related to improved railroad car brake control valves and particularly to such improvements as relate to the adverse effects of vibration on piston valves and the like.
With the trend toward light-weight railroad cars, such as aluminum coal hopper cars, for example, relatively severe vibration can occur when such light-weight cars are operated under less than ideal dynamic conditions. Wheel surface irregularities including out-of-roundness, worn truck components, and poor rail conditions are believed to contribute to such dynamic operating conditions that result in severe vibration of the brake control valve on the car.
Presently, the industry standard ABD, ABDW and ABDX brake control valves employ many moving parts including piston members that are made from aluminum, as well as non-moving parts such as aluminum valve covers and the like. Such high repetitive metal-to-metal contact between these aluminum parts, as may be induced by severe vibration, has been found to cause abrasive wear of the contacting parts. Such abrasive wear results in the accumulation of a fine, oxidized aluminum powder which migrates into the service piston assembly and absorbs the slide valve lubricant, leaving a rather thick, dry residue. Such loss of lubrication results in high slide valve friction, with high operating pressure differentials, and consequently erratic and unacceptable behavior of the aforementioned control valves.